1. Newton’s Second Law
F = ma

2. Second Law
The net force of an object is equal to the product of its mass and acceleration, or F=ma.

3. Everyone unconsciously knows the Second Law
Everyone unconsciously knows the Second Law. Everyone knows that heavier objects require more force to move the same distance than it does lighter objects.

4. Newton’s Second Law of Motion
Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).
Who pushed the rock up
the hill in mythology?

5. What does this mean?
This also tells us that a larger mass will have a smaller acceleration than a smaller mass if the net forces are equal on both masses.
Force is directly proportional to mass and acceleration. Imagine a ball of a certain mass moving at a certain acceleration. This ball has a certain force.
Now imagine we make the ball twice as big (double the mass) but keep the acceleration constant. F = ma says that this new ball has twice the force of the old ball.
Now imagine the original ball moving at twice the original acceleration. F = ma says that the ball will again have twice the force of the ball at the original acceleration.

6. Doubling the force doubles
the acceleration.
Doubling the mass but
keeping the same force
decreases the acceleration
So what if you decrease the mass by half?
How much force would the object have now?
What about doubling the force AND the mass?

7. Newton’s 2nd Law & Force of Gravity
Everyone has heard of the FORCE of gravity We know gravity is a force in nature: Gravity: the force that pulls objects towards each other Since gravity is a force it also obeys Newton’s second law F=ma
Since objects fall at the same speed, their acceleration is the same.
All objects accelerate at the same rate. Here on Earth the rate is:
Ag= 9.8 m/s2 or
Ag= 32 ft/s2

8. F = ma basically states that the force of an object depends on its mass and its acceleration.
Something very massive that’s changing speed very slowly, like a glacier, can still have great force.
Something very light that’s changing
speed very quickly, like a bullet, can
still have a great force.
Something very small changing
speed very slowly will have a
very weak force.

9. Newton’s 3 Laws of Motion
Newton’s Second Law of Motion aka F=ma
Force = mass x acceleration
Can be written as:
F=ma ; a= F/m ; m= F/a
What is the basic unit for mass in F = ma? Kilogram
What is the basic unit for acceleration? Meter/sec/sec
Therefore the basic unit for Force is
(kilogram)( meter/sec/sec)
An object with a mass of 1 kg accelerating at 1 m/s/s has a force of 1 Newton

10. Second Law (F = ma)
How much force is needed to accelerate a 1400 kilogram car 2 meters per second/per second?
1. Write the formula
F = m x a
2. Fill in given numbers and units
F = 1400 kg x 2 m/sec/sec
3. Solve for the unknown, with units
2800 kg-m/s/s or 2800 N

11. Force
A force is any influence that can cause an object to be accelerated.
The pound (lb) is the unit of force in the British system of measurement:
1 lb = 4.45 N or
1 N = lb

12. Newton’s 2nd Law & Weight
F=ma
Weight is the force of gravity acting on an object’s mass.
Therefore weight is a type of Force
The formula for weight: Weight = mass x Ag
Since Ag= 9.8 m/s2 then
Weight = mass x 9.8 m/s2
Remember:
1 newton = 0.22 pounds

13. Different masses?
Newton’s 2nd Law proves that different masses accelerate to the earth at the same rate, but they hit the ground with different forces.
98 N
9.8 N